Method of producing crude metal



3,102,87 METTTGD OF PRUDUCTNG CRUDE METAL Douglas S. Chishoim, Midland, Mich., assignor to The Dow Chemical Company, Midiaud, Mish., a Corporation ot Delaware Filed Feb. 3, 1953, Ser. No. 712,'789 9 Ctaims. (Ci. 'T-34.1)

' The invention concerns the production of crude metals which are reducible from compounds containing them by the action of magnesium metal thei-con. It more particularly concerns the reduction `of a subgroup' lVa metal halide to produce a subgroup IVa metal in a crude state ne i ducible by the interaction therewith of mzagnesium for an economical method of producng a crude feed containing such a metal suitable for refinng in an electrolytic cell.

The Principal object of the invention, theretore, is to provide an apparatus for and a method of producing 'metals, particularly subgroup IVa `rnetals, having a halide rcducble by' the interaction thereof With magnesium,

u which are useful as feed in an electrorefining cell. A

suitable for further refining by electrolysis in a fused i salt bath. i

Methods of producing subgroup IVa metals, viz., titanium, hafnium, zirconium, and thorium in a sufficiently pure state for alloying and fabricating, are known.

However, known methods are costly due to the highly V reactve nature of subgroup IVa metals, thereby making such metals uneconomical for a number of uses for which their special properties make them highly desirable.

Methods of producing a refined subgroup IVa metal by eiectrolysis of crude metal are known. Among such methods is the method of producng refined titaniurn from crude titanium feed described in the United States Bureau of Mines, Report oi Investigations, Number 5315 (February 1957) The method therein described empioys an electrolytic cell` for producing refined titanium from off-grade sponge and scrap containing appreciable percentages of titanium. Such a cell as therein described illustrates the type of electrolytc cell for which crude feed in the form of sponge and scrap containing not over about 9 to 10 percent contaminants is usable to produce a metal of satisfactory purity for general use. The Brnell hardness number` of titanium, for example, was reduced from 314 to 78 by being electrorefined or electropurified in the cell described in said Bureau of Mines Report.

'Ihe method of employing the cell described iuthe aforesaid report consists chiefiy of passing DC. through a fused salt electrolyte which has immersed therein a e conducting cathode and a crude titanium anode, under an inert gas atmosphere, Wherein the crude titanium anode is gradually consnmed by the ensuing electrolytic action, refined titanium collecting at the cathode and the impurities collecting as a sludge at the bottom of the electrolytc charnber.

Crude subgroup IVa metals of a purity of 89 to 91 percent are quite satisfactory for further refining in electrolytic cells generally and particularly in the cell described above. Methods of preparing crude feed for use in this type of cell have not heretofore` been economically satisfactory, either because the preparatory process was too costly or the titanium -feed Was purer than that necessary or it was not pure enough for subsequent economical refinement in the electrolytic cell. Particularly noteworthy of a method not proving satisfactory for the production of such crude subgroup lVa metal, because the crude metal is not sufficiently pure, is that cornprising, the reduction of an ore containing an oxide thereo f lay-'heating it With carbon. i

A desderatum then eXists in the art of producing subgroup IVa metals and other metals having halides remore specific object is to provide a method of producing crude titanium metal for use as feed in the electrorefining cell of the type described in the-United States Bureau of Mnes Report of Investigation, Number 5315.

The method by which these and related objects of the invention are attained is made clear in the following description with reference to the annexed drawing and is particularly dened in the appended clairns..

The invention is a method of preparing crude metals, especially subgroup IVa metals, having a halide reducible by magnesium metal to produce thereby suitable feed for refinng in an electrolytic cell. The method consists essentially of superimposing molten magnesium on a molten saline flux of a greater densty than the molten mag nesium, passing a halide of the metal (to be produced) as a gas up` through the molten ux into the molten mag. nesiurn thereby producing a sludge which contains the metal to be produced, removing the sludge thus produced -from the fiux, and thereafter leachirg it to recover therefrorn the crude metal, eg., ,a subgroup -IVa metal, which contains not over 9 to 11 ;peroent impurites.

The drawing is a sectional elevation of an apparatus useful in practicing the method of the invention.

The production of titanum will be described for the purposes of illustrating the practice of the invention, but the practice of the invention is not limited thereto. Other metale having a halide reducible by the action of magnesium thereon fall within the scope of the inventior;`

In carrying out the invention,- a saline flux of greater density than molten magnesiurn is placed in a suitable pot mid melted. i Magnesiurn metal is placed thereon and also melted., magnesium then forrnng a superimposng layer on top of the lux. A titanium halide which is Volatile at the temperature of the fiux is passed up through the flux into the molteu magnesium as a gas according to`the United States Patent 2,779,672. The halide may be admtted as a liquid or solid so long as it uolatilizes upon contact With the molten flux. Unlike the method described in said patent, however, which has for its purpose the purification of magnesium, the method of the instant invention requires that the titaniurn halide,' preferably TiCl be passed up through the fiux and into the molten magnesium beyond the time required tor purification of the magnesium metal for a period of time suiciently long for the TiCl to ully react with. the magnesium metal to form Ti metal and Mgcl -Sludge forms and settles to the bottom of the fiux, forming the intermediate product of the invention, from which crude: titanum metal is thereatter produced by leaching said sludge to produce crude Ti metal useful in producing titaniun metal of high purity by electrolysis in an electrorefinng cell. The sludge continues to be formed so longas the halide, eg., TiCl is passed into the magnesium metal thus superimposed on the flux. Magnesium halide, eg., Mgcl is formed as a lay-product in the sludge thereby consuming magnesium metal in the process. `As a result thereof, magnesiuun metal must be added at intervals to the reaction vessel. The sludge may be removed by manual operation, as by scooping or dipping it out, or it may be continuously removed by an anger, a conveyor arragement, or by other suitable mechanical handling means.

The sludge thus removed contains at least about 60` percent and usually at least 65 percent titanium and usually between about 28 and 32 percent water-soluble contaminants. After removal, the sludge is preferably comminuted. Thereafter, it is leached, preferably with an aqueous acid solution, eg., a 1 to 10 percent and preferably about a percent by weight aqueous HCl, until the impurities do not exceed about 11 percent. It is then ready for use as raw feed for further refining in an electrorefining or purification cell.

Apreferred mode of practicng the invention is to employ the apparatus of the invention shown in the drawing.

The' drawing shows an apparatus oomprising a gas-fired furnace setting 10, cast steel melting pot '12 supported theren, removable hollow torus 14 having a downwardly extending open face 15 positioned substantially horizontally in pot 12 intermediate its top and bottom, titanium halide feed duct 16, extending into the pot with open end 17 below torus face 15, and scraper 18 which is rotatable by means 'of arm 19 which extends downwardly through the axis of 18 substantially centrally of torus 14. Scraper blade 18 is shaped so that its upper edge matches the transverse :section of underside 23 of torus 14. Gas burner 20 at opening 21 and gas o utlet 22 provide a means for heating pot 12 and for venting combustion gases, 'respectively Torus 14 is supported by brackets 24 and 26. Ar'm 19 of scraper '18 may be turned manually or can be turned by a train of gears, a belt, or the like attached to a source of mechanical power (not shown).

The following example illustrates the practice of the invention employing an'apparatus :of the type shown in the drawing. MgCl was placed in melting pot 12 and melted by raising the temperature above its me lting point by burning gas introduced at opening 21 in furnace setting 10.' The level of the melting MgCl is above the torus as shown at 27. Downwardly opening hollow torus IA was then placed in the molten 'MgCl at level 28. Magnesium metal pieces in the form of about 1 pound ingots were thenplaced in the MgCl below the open face of torus 14 by means of tongs and there released, whereupon they rose to the' surface of the MgCl in the aforesaid hollow cavity in torus 14 thereafter floating on the surface of the MgCl as item 29 in the toroidal cavity displacing sufiicient MgCl to accommodate the Mg metal pieces, whereupon they melted; Trapped air in the cavity was substantially also displaced at this time; any remaining air reacted with magnesium metal and/ or titanium and became an impurity in the sludge being formed. TCL; was introduced as a liquid through tube 16. The TiCl gasified in tube 16 and entered the Mgcl flux as a gas and thereupon bubbled up to underside 23 of torus 14.

to the method of the mvention contained 90.2 percent titanium. This is a satisfactory feed to empl-oy in an electrolytic cell of the type described in the Bureau of Mines electropurification cell described hereinabove.

Advantages flowing from the inventiorare shown by the example which economically produced crude titanium feed without the need for inert gas or provision of elaborate measures to prevent contamination. I The crude titanium is fully satisfactory for further refining to a low Brinell hardness, high-purity titanium in an electrolytic cell.

Having described the invention, what is claimed and desired to be protected by the Letters Patent is:

1. The method of producing a crude metal having a tetrahalide reducible by molten magnesium metal which comprises positioning a hollow torus, having an open face directed downward, below the level of a body of molten salt 'of greater density than molten magnesium selected from -the class consisting of an alkali metal halde, an alkaline earth halide, and a mixture thereof; introducing pieces of magnesium metal into the molten salt below the open face of said torus; melting the magnesium metal and displacing molten salt from the torus thereby forming a contacting surface with said molten salt therebelow; introducing a gaseous tetrahalide of the metal to be produced in an amount suflicient to react with substantally all the molten magnesium metal; allowing the tetrahalide to contact the The rate of feed of TiCl was regulated so that substantially all of it reacted with the rnagnesium metal confined within torus 14. The reaction with the magnesium built up a loosely adherent sponge on underside 23 of the torus neces'stating periodic removal by turning arm 19 so as to activate scraper 18. The sludge thus loosened fell to the bottom of the pot, as represented by item` 30 of the drawing, from whence it was periodcally removed bytladling it out. The thus-removed sludge was then cast into molds.

When the titanium in the molds was cooled, it was removed, crushed and placed in a drum provided with an agtator and containing water which had been acidified with HCl to a 2 percent by weight solution. The sludge was then washed under agitaton in the HCl solution. Watersoluble im-purities were thereby removed. After twentyand dried. The crude titanium thus produced according molten magnesium metal in said torus at a point directly below the open face of the torus to efiect a reduction of the tetrahalide by the magnesium metal to yield a reaction product containing metal reduced from the halide, at least a portion of which adheres to the arcuate inner walls of the torus; removing such adhering reaction product by a revolving scraper means and causing the reaction product to accumulate in the lower part of the molten salt; removing the reaction product from the salt; and thereafter subjecting the' thus removed reaction product to the leaching action of an -aqueous solution containing at least one percent by weight of HCl.

2. The method of producng a crude metal having a tetrahalide reducible by molten magnesium metal which comprises: suspending solid pieces of magnesium metal within a confining means below the level of a molten salt 'bath having a greater density than the molten magnesium metal and being maintained at a temperature above the melting point of magnesium metal, thereby creating a reaction zone which is closed to communication upwardly and open to communication downwardly so that the magnesium metal displaces molten salt from said reaction zone and forms, when melted, a contacting surface -with said molten salt therebelow; confining the molten magnesium metal in said reaction zone Suspended in saidmolten salt bath; continuously admitting a tetrahalide of the metal to be produced, in the gaseous state, into the salt bath at a point substantia-lly directly below the thus confined molten magnesium metal in an amount sufiicient to elfect a reaction with a substantial proportion of the molten magnesum metal in the reaction zone; allowing the tetrahalide to contact the molten magnesium metal in said reaction zone -to produ'ce a sludge having a density greater than the molten salt and containing the metal reduced from the tetra- 'la-lide; collecting the sludge thusproduced in the lower part of the molten salt bath; removing the sludge from the bath; and leaching the so removed sludge with an aqueous solution of a mineral acid. i

3. The method of claim 2 wherein the said tetrahalide is TiCl The method of claim 2 wherein said tetrahalide is Zr 14.

S. The method 'of claim 2 wherein the sludge is leached V 8. The method of claim 2 wherein the aqueous solution of a mineral acid is 1 to 10 .percent HCI hy weight.

9. The method of claim 2 wherein the cross-section of i said zone is an inverted U-shape and the lineal dimension References Cited in the file of this patent UNITED STATES PATENTS Freudenberg Feb. 21, 1939 6 Kroll June 25,1940 Blue Sept. 11, 1951 Winter Aug. 19, 1952 Chisholm et al Jan. 29', 1957 McMackn e-t al Aug. 27, 1957 Olson Nov. 12, 1957 Najarian June 24, 1958 Lee et al. Dec. 16, 1958 

2. THE METHOD OF PRODUCING A CRUDE METAL HAVING A TETRAHALIDE REDUCIBLE BY MOLTEN MAGNESIUM METAL WHICH COMPRISES: SUSPENDING SOLID PIECES OF MAGNEISUM METAL WITHIN A CONFINING MEANS BELOW THE LEVEL OF A MOLTEN SALT BATH HAVING A GREATER DENSITY THAN THE MOLTEN MAGNESIUM METAL AND BEING MAINTANED AT A TEMPERATURE ABOVE THE MELTING POINT OF MAGNESIUM METAL, THEREBY CREATING A REACTION ZONE WHICH IS CLOSED TO COMMUNICATION UPWARDLY AND OPEN TO COMMUNICATION DOWNWARDLY SO THAT THE MAGNESIUM METAL DISPLACED MOLTEN SALT FROM SAID REACTION ZONE AND FORMS, WHEN MELTED, A CONTACTING SURFACE WITH SAID MOLTEN SALT THEREBELOW; CONFINING THE MOLTEN MAGNESIUM METAL IN SAID REACTION ZONE SUSPENDED IN SAID MOLTEN SALT BATH; CONTINUOUSLY ADMITTING A TETRAHALIDE OF THE METAL TO 